I've replaced rack and pinion twice, pump, pressure switch and flushed with Mercon V. Idk what else to replace except the hoses but there isn't a leak in the system. Van has 155k if that makes a difference. Original issue would come and go. Finally never came back so I checked to see if fluid was low, fluid was black. I proceeded to change out the fluid first with no luck. Pump never whined so I next replaced the RnP. I kept switching everything out, but still no luck. If you can think of anything else to check for please comment below.
thanks in advance.

 

What is your actual symptoms? Have you checked the steering shaft knuckle (U-Joint) as it sets when it can get covered with eternal crud? When the U-Joint gets bad, it makes it hard to turn the wheels because it is binding. It also will not allow the wheels to return to center after a turn. Spray the U-Joint with some lube to see if the issue goes away. If it does, a new one is needed. It sets just above the rack. It's fairly easy to replace.